Why the East Coast Is Seeing Summer in Spring

Abnormally warm temperatures brought a taste of summer to the eastern part of the United States on Monday (April 16), testing runners resolve in the Boston Marathon and bringing out sunbathers in New York.

"It's just the extreme warm spring weather pattern continuing," said Mike Pigott, a senior meteorologist at AccuWeather.com, referring to record-breaking weather in the continental U.S. last month.

In Boston, temperatures were about 20 degrees Fahrenheit (11 degrees Celsius) higher than the normal high when runners set out this morning, said Pigott. Meanwhile, in New York City, temperatures hit 86 degrees F (30 degrees C) in Central Park. By comparison, the normal high is 62 degrees F (17 degrees C), Pigott said.

While the eastern two-thirds of the lower 48 states have seen unusual warmth so far this year, the west has had a cooler, wetter experience. On Monday (April 16), San Francisco was 2 degrees F (1 degree C) below normal.

"One of the reasons that we have been so warm this spring is most of the cold fronts we see at this time of year have been diving down into the western U.S.," Pigott said.

The configuration of the jet stream, a band of high-altitude westerly winds, is responsible, and this year, it is directing colder air and storm systems into the West Coast while allowing high pressure and warmer temperatures to prevail in the East, he said. [A Warm Winter: Is It Climate Change?]

Early last year, the opposite scenario played out with wet, cold weather arriving over the East, and drier weather over the West, culminating in a devastating drought.

On Monday (April 16), temperatures in the middle of the country, in places such as Wichita, Dallas and St. Louis, were around normal. In the far southeast, Tampa, Fla., was a few degrees above normal, Pigott said.

Wynne Parry

Wynne was a reporter at The Stamford Advocate. She has interned at Discover magazine and has freelanced for The New York Times and Scientific American's web site. She has a masters in journalism from Columbia University and a bachelor's degree in biology from the University of Utah.